Process for the preparation of linear thermoplastic polyesters with freezing temperatures above 100u deg. c.



United States Patent 7 Claims. (Cl. 260-47) It is known that linearpolyesters which are prepared 1 from aromatic dicarboxylic acids orreactive derivatives of these acids and bivalent phenols have excellentand technically very desirable properties. They distinguishadvantageously over the equally known polyesters made on a large scalefrom aromatic dicarboxylic acids and certain aliphatic diols,particularly due to their much higher freezing temperatures. Thesesurpass not only those of the known polyalkylene terephthalates, butalso those of almost all other known thermoplastics. From suchpolyesters formed by the reaction of aromatic dicarboxylic acids andbivalent phenols there may, therefore, be prepared shaped articles, suchas fibers, films, coatings, and other molded bodies, which areutilizable up to temperatures of about 170 to 200 C., depending upon theselection of the monomers used in their preparation and the mixingratios thereof.

A number of processes have been proposed for the production of suchpolycondensates, all of which involve,

however, considerable difiiculties with regard to process techniques ifthe preparation of these polymers is to be carried out at a scale largerthan that of the laboratory.

Thus, linear polyesters have already been prepared by Bischotf andHedenstroem by the transesterification of diacetates of bivalent phenolswith dicarboxylic acids. Subsequent researchers have obtained merelydarklycolored products with this process.

Furthermore, it has been proposed to heat dicarboxylic acid halides withbivalent phenols in high-boiling, inert solvents, whereby solutions ofthe corresponding polyesters resulted with the cleavage of hydrogenhalide from which solutions the latter had to be isolated byprecipitation and repeated re-precipitation. Aside from the cumbersome,complicated isolation of the polymers, this process involves theadditional disadvantages that working must be carried out with theabsolute absence of water and with extremely purified startingsubstances, and that the cleavage of hydrogen halide creates a series ofadditional technicaldifliculties.

Another possibility for the preparation of these polyphenyl estersresides in the use of the contact surface condensation process accordingto which solutions of dicarboxylic acid halides in organic solventsimmiscible with water are brought into contact with aqueous solutions ofalkali metal salts of bivalent phenols. The polymer is thereby obtained,with the cleavage of alkali halide, on the contact surfaces of the twophases which are not miscible with one another. Although this process isof great importance for the preparative production of suchpolycondensates, it seems hardly suitable for technical purposes, sincerelatively very large quantities of solvents have to be employed ifsufiiciently high degrees of polycondensation are to be attained.Moreover, reproduction of the polycondensation degrees once achieved isseldom possible, even if all of the variables of the reaction aremaintained as constant as possible.

Furthermore, phthalic and isophthalic acid as Well as dimethylterephthalate have already been esterified and, respectively,trausesterified with bisphenol A (p,p-dihydroxy-diphenyl-dimethylmethane) with a view toward 3,399,170 Patented Aug. 27, 1968 or with theaim of preparing the corresponding polyphenyl esters, whereby, however,only darkly-colored, low molecular, horn-like masses were obtained aftera reaction time of 30 and, respectively, 74 hours.

For the preparation of some specific polycondensates, the aryl esters ofaliphatic dicarboxylic acids have also been reacted with diphenols, ifdesired in mixture with dialcohols, whereby light, high molecularproducts were obtained with the use of a suitable reaction procedure.

The polyphenyl esters treated most frequently heretofore because of theeasy accessibility of the starting materials are those which are derivedfrom terephthalic acid, isophthalic acid and mixtures of these acids aswell as from bisphenol A. While the polyesters containing only one ofthe two dicarboxylic acids should hardly claim any technical interestbecause of their very high melting points and low solubility, thosepolyesters which are made from mixtures of these two acids have a numberof highly desirable properties, such as freezing temperatures betweenabout and C., melting points between about 220 and 330 (3., excellentelectrical resistance values, excellent abrasion resistance, solubilityin different solvents graduated according to the composition, andremarkable resistance against thermal decomposition.

Similarly, valuable properties have become known also for linearpolyesters which are made from mixtures of terephthalic acid andisophthalic acid derivatives, hydroquinone as well as resorcinolpyroatechol, and o,o'-dihy droxybiphenyl or mixtures of the threelast-mentioned compounds. Although such polyphenyl esters possess inpart melting points considerably below the temperature at which athermal polycondensation reaction is still possible in view of the heatstabiilty of the monomers and the polycondensates, it is neverthelesspractically impossible to prepare them according to one of thetechnically customary melting condensation processes. This is due to thefact that these polycondensates assume a rubber-like consistency abovetheir melting temperature as soon as their mean polycondensation degreehas increased to a certain value. This minimum polycondensation degreemust, however, be exceeded if technically valuable polymers are to beobtained. In all of the polyphenyl esters examined, it is of the ordercorresponding to a viscosity number (measured in phenol/tetrachloroethane 60:40% by weight at 25 C.) of about 0.45 to 0.5. Whilepolyphenyl esters still meltable at a condensation temperature of about320 C., which temperature is still permissible, as experience has shown,have--up to the minimum polycondensation degree described in more detailhereinab0vea melting viscosity which still allows stirring of the mass,stirring as well as the discharge of the molten mass from the reactionvessel become practically impossible once this minimum polycondensationdegree has been exceeded. If the polycondensation reaction isinterrupted while the mass is still in a stirrable condition, merelybrittle products will therefore be obtained which have no particulartechnical significance, whereas only above this minimum polycondensationdegree, which cannot, however, be exceeded in the conventionalpolycondensation apparatus, will hard, ductile and elastic polyphenylesters be yielded. Accordingly, such polycondensates were heretoforethermally prepared only in the presence of high-boiling solvents whichhad to be removed again subsequently and purified in a complicatedmanner.

It has now been found that valuable polycondensates which may beprepared also at a technical scale without particular ditliculties maybe obtained by heating aryl esters of tereand/ or isophthalic acid withequimolecular amounts of a mixture of from about 90 to 70 mol percent ofa diphenol and about 10 to 30 mol percent of a dialcohol in the presenceof conventional polycondensation catalysts and in the absence ofsolvents, while discharging easily volatile reaction products, for suchlengths of time until a product having a viscosity number above about0.5 has been formed.

alcohol ester groups), the reaction is preferably carried out with aslow as possible an excess of hydroxyl compounds. It has further beenfound that the alcoholysis of the aryl esters takes place quickly andquantitatively For example, the phenyl-, cresyl-, xylenyland naph- 5 ata temperature below the boiling point of the phenolic thyl esters may beutilized as aryl esters of tereand/ or components of the aryl esters.The preferred mode of isophthalic acid. carrying out thetransesterification and polycondensation The phenyl esters areparticularly easily accessible acreaction is, therefore, as folows:cording to the process described in copending patent An equimolecularmixture of the dicarboxylic acid application Ser. No. 257,870, filed onFeb. 12, 1963, now diaryl esters, on the one hand, and the mixture ofthe US. Patent 3,356,712. diphenols and dialcohols, on the other, isreacted with For example, bisphenol A, resorcinol and hydroquinonecatalytic amounts of one of the known compounds for are used asdiphenols in accordance with the present accelerating thetransesterification and polycondensation invention. reaction, preferablyantimony trioxide, and heated under The dialcohols are, for example,glycols, such as ethylnitrogen at normal pressure up to a temperature atwhich one glycol, hexanediol-1,6, and hexahydro-p-xylylenethe contentsof the flask is just about liquefied. This temglycol. perature ismaintained for about 15 to 30 minutes,

While, as a result of the inclusion or incorporation of which-asexperience has shown-will suffice for the aliquot parts of bivalentalcohols, the thermal behavior, complete alcoholysis of the amount ofthe diaryl esters and particularly the freezing temperature, isunfavorably equivalent to the dialcohol. Thereafter, the temperatureinfluenced as compared to the corresponding pure polyis increasedrapidly and, as soon as necessary, a gradual phenyl esters, the meltingviscosity of the polycondensates evacuation simultaneously made so thatthe easily volais, on the other hand, reduced to such an extent thattheir tile aryl compound cleaved off the diaryl esters distills offpreparation in the apparatus conventional for the producpromptly. Thetemperature is finally increased to about tion of polyesters may takeplace and be carried out with- 300 C. and maintained at that value whilethe pressure out the concomitant use of difficulty separable solvents.is reduced to below about 0.5 torr. Temperature and vacu- Anotheradvantage of the polyesters modified in accordurn are maintained forsuch length of time as is necessary ance with the present inventionresides in that, in conuntil the desired degree of polycondensation hasbeen trast to the known and pure polyphenyl esters not modireached. fiedby bivalent alcohols, they may be further treated not Of course, it isalso possible to transesterify the dialcoonly by pressing and fromsolution, but also by extruding hols in a first step or stage with apart or the entire and injection-molding. These advantages may beattained amount of the dicarboxylic acid diaryl esters, to isolate witha suitable selection of the diphenol-dialcohol-ratio thetransesterification product, and to continue the transwhile notproducing a decrease of the freezing temperaesterification reactionafter the admixture of the required ture of the polycondensates made inaccordance with the quantity of diphenol. This process, however, is morecompresent invention below that of the bisphenol A-containplicated anddoes not afford any visible advantages as ing polycarbonates, which areparticularly remarkable in compared to the above-described, one-stepprocess. this regard. It is an object of the present invention,therefore, to

Depending upon the composition thereof, the polyesprovide a process forthe production of linear, thermoters made in accordance with the presentinvention are plastic polyesters. either crystalline or amorphous,extensible above their It is a further object of the present inventionto produce freezing temperature according to conventional processes,such polyesters having a freezing temperature above and may be used forthe manufacture of fibers, films and about 100 C. other molded bodies.They are soluble in strongly polar Other objects wil become apparentfrom the detailed solvents, for example, in cresols, and theirsolubility in description of the present invention hereinbelow whereinother solvents, such as chlorinated hydrocarbons, ketones, the examplesserve to illustrate the present invention withesters, etc., may bevaried as desired by the selection of out, however, limiting the same.the starting materials employed in the preparation thereof. Thefollowing examples were carried out according to The polyesters to beprepared according to the present the one-step process describedhereinabove.

EXAMPLES 1-9 Example No 1 2 3 4 5 6 7 g 9 Com osition:

(mol percent) 25 T (mol percent) 25 B (mol percent)-. 35

G (mol percent) 15 Viscosity number. 0. 610

Freezing temp., 114

Beginning of melt, 0.. 135

End of melt, 0 180 invention are produced by heating approximatelyequivalent amounts of diaryl esters of terephthalic acid or isophthalicacid or mixtures of diaryl esters of these acids with a mixture ofdiphenols and dialcohols, which consists of approximately to 90 molpercent diphenols and about 30 to 10 mol percent dialcohols, in thepresence of a transesterification and a polycondensation catalyst underinert gas and subsequently under vacuum. The diaryl esters employed arepreferably those of relatively easily volatile aryl compounds, such asthe phenyl or cresyl esters.

It has been found that the polycondensates will be lighter in color thesmaller the concentration of free phenolic hydroxyl groups in the melt.Since alcoholic hydroxyl groups may, under the reaction conditions,cleave phenyl ester groups (but phenolic hydroxyl groups not In theabove table, I designates the isophthalate and T the terephthalate unitsof the mixed polyesters; B the units of bisphenol; and G the units ofethylene glycol. The isophthalate and terephthalate units were employed,in the preparation of the polyesters, as the diphenyl esters of theseacids. The con densate corresponding to Example 4 could not be obtainedwith a high molecular property due to too high a melting viscosity. Theviscosity numbers were determined in the usual manner on the basis ofphenol-tetrachloroethane solutions (60:40 weight percent at 25 C. Thefreezing temperatures were measured by means of a penetrometer accordingto Edgar & Ellery [1. Chem. Soc., 2633 and 2636 (1952)! and the meltingrange was measured by visual observation of the samples under a heatingtable microscope.

The melting viscosity could not be determined for experimental reasons.In all the cases where 20 mol percent of the bisphenol had been replacedby glycol, it was sufficiently low to render possible rising oflocked-in gas bubbles at 300 C. from molten, semispherically-shapedmolded bodies having a surface diameter of about 5 cm., and became lowerwith an increasing glycol proportion, as was to be expected. The mixedpolycondensates showed an improved solubility in different solvents andsimultaneously therewith a reduced tendency to crystallization ascompared to the known pure polyphenyl esters having the same compositionexcept for the glycol constituent.

EXAMPLES -15 In the following examples, the influence of the exchange ofethylene glycol against other aliphatic diols on the characterizing dataof the poly-condensates is examined on the basis of products composedaccording to Examples 4-6.

Example No 10 11 12 13 14 15 Composition:

I (mol percent) 25 25 25 25 25 T (mol percent). 25 25 25 25 25 25 B (molpercent) 45 40 45 35 H (mol percent) 5 10 15 X (mol percent). 5 10 15Viscosity number. 0.590 0. 622 0. 630 0.650 0. 633 0.61 Freezing temp.,C 155 142 125 148 135 109 Beginning of melt, 190 187 155 179 160 128 Endof melt, C 250 225 194 235 215 168 In the examples compiled hereinabove,I, T and B have the meaning specified further hereinabove in Examples1-9; H designates hexanediol-1,6 and X is hexahydro-p-xylene glycol.Examples 10 to 15 show that the freezing temperatures as well as themelting ranges in a first approximation are independent of the chemicalconstitution of the dialcohol compound used.

EXAMPLES 16-21 In the following examples, the influence of the exchangeof bisphenol A against other aromatic diphenols is examined.

In the above table, I and G have the meaning indicated hereinbefore, andR and C are resorcinol and hydroquinone, respectively. In the case ofExample 19, no sufficiently highly condensed product could be obtaineddue to the melting viscosity which was still too high at the reactiontemperature.

Examples 16 to 21 also show that the influence of the exchange ofbisphenol A for other easily accessible diphenols on or with regard tothe thermal properties of the polymers obtained is relatively slight.

While the invention has been described with reference to a number ofexamples thereof, it will be understood that changes may be made incarrying out the process without departing from the scope of theinvention, and it is intended that all matter contained in the abovedescription shall be interpreted as illustrative and not in a limitingsense.

We claim:

1. A process for the preparation of linear, thermoplastic polyestershaving freezing temperatures above 100 C. which consists of heating amixture consisting of equimolecular amounts of (A) an aryl esterselected from the group consisting of the phenyl, cresyl, xylenyl andnaphthyl esters of terephthalic acid, isophthalic acid and mixturesthereof with (B) a mixture consisting of between approximately 90 andmol percent of a diphenol and between approximately 10 and 30 molpercent of a glycol in the presence of a polycondensation catalyst andin the absence of a solvent for such a length of time and whiledischarging easily volatile reaction products until a product has beenformed having a freezing temperature range of about 109-158" C. and amelting point range of about 128-250 C.

2. A process as defined in claim 1, wherein the diphenol-glycol ratio isso chosen that the molten polycondensate possesses the sufficiently lowmelting viscosity required for its preparation.

3. A process for the preparation of linear, thermoplastic polyestershaving freezing temperatures above 100 C. which consists of heating 'amixture consisting of equimolecular amounts of (A) an aryl esterselected from the group consisting of the phenyl, cresyl, xylenyl andnaphthyl esters of terephthalic acid, isophthalic acid and mixturesthereof (B) a mixture consisting of between approximately and and 70 molpercent of a diphenol and between approximately 10 and 30 mol percent ofa glycol in the presence of a transesterification and polycondensationacceleration catalyst and under an inert atmosphere to a temperature atwhich said aryl ester and said (B) mixture are about liquefied for aperiod of time sufificient for the essentially complete alcoholysis ofthe amount of diaryl ester equivalent to the amount of glycol, andthereafter increasing the temperature and evacuating the volatile arylcompound cleaved off the diaryl ester, and then maintaining thetemperature at about 300 C. While reducing the pressure on the reactionmixture to below about 0.5 torr and maintaining the same until theformation of a product having a freezing temperature range of about109-158 C. and a melting point range of about 128-250" C.

4. A process as defined in claim 1, wherein said aryl ester is thediphenyl ester.

5. A process as defined in claim 3, wherein said aryl ester is thediphenyl ester.

6. A process as defined in claim 1, wherein said diphenol is selectedfrom the group consisting of bisphenol A, resorcinol and hydroquinoneand said glycol is selected from the group consisting of ethyleneglycol, hexanediol- 1,6 and hexahydro-p-xylylene glycol.

7. A process as defined in claim 3, wherein said diphenol is selectedfrom the group consisting of bisphenol A, resorcinol and hydroquinoneand said glycol is selected from the group consisting of ethyleneglycol, hexanedio1-1,6 and hexahydro-p-xylylene glycol.

References Cited UNITED STATES PATENTS 3,067,169 4/1962 Krimm 260-47 XR3,143,526 8/1964 Caldwell et al. 26047 2,989,501 6/1961 Stamatoif260-476 FOREIGN PATENTS 902,021 7/1962 Great Britain.

914,886 1/1963 Great Britain.

924,607 4/1963 Great Britain.

WILLIAM H. SHORT, Primary Examiner.

LOUISE P. QUAST, Assistant Examiner.

1. A PROCESS FOR THE PREPARATION OF LINEAR, THERMOPLASTIC POLYESTERSHAVING FREEZING TEMPERATURES ABOVE 100* C. WHICH CONSISTS OF HEATING AMIXTURE CONSISTING OF EQUIMOLECULAR AMOUNTS OF (A) AN ARYL ESTERSELECTED FROM THE GROUP CONSISTING OF THE PHENYL, CRESYL, XYLENYL ANDNAPHTHYL ESTERS OF TEREPHTHALIC ACID, ISOPHTHALIC ACID AND MIXTURESTHEREOF WITH (B) A MIXING CONSISTING OF BETWEEN APPROXIMATELY 90 AND 70MOL PERCENT OF A DIPHENOL AND BETWEEN APPROXIMATELY 10 AND 30 MOLPERCENT OF A GLYCOL IN THE PRESENCE OF A POLYCONDENSATION CATALYST ANDIN THE ABSENCE OF A SOLVENT FOR SUCH A LENGTH OF TIME AND WHILEDISCHARGING EASILY VOLATILE REACTION PRODUCTS UNTIL A PRODUCT HAS BEENFORMED HAVING A FREEZING TEMPERATURE RANGE OF ABOUT 109-158*C. AND AMELTING POINT RANGE OF ABOUT 128-250*C.